Apparatus and method for coating pipe



Nov. 16, 1965 J. H. LEMELSON APPARATUS AND METHOD FOR COATING PIPE Original Filed May 28, 1956 W W m 5 TM WM M ma 4% m Z w (M w. 4

3,218,134 APPARATUS AND METHOD FOR COATING PIPE Jerome H. Lerneison, 289 High St, Perth Amboy, NJ. Original application May 28, 1956, Ser. No. 589,848, now Patent No. 3,166,829. Divided and this application Apr. 28, 1961, Ser. No. 112,148

Claims. (Cl. 11718) This application is a division of my copending application Serial No. 589,848 entitled Ducted Sheeting Construction, filed on May 28, 1956, now US. Patent No. 3,166,829.

This invention relates to an apparatus and method for coating pipe, tubing, or other elongated hollow articles with thermoplastic particulate materials, and more particularly to such an apparatus and method for app-lying the thermoplastic material to the article to be coated from suspension in a fluidized bed.

Particulate plastic materials have been applied as coatings to various articles by immersing such articles, heated to temperatures in excess of the melting points of the coating materials, within fluidized beds formed in suitable containers. Such beds are conventionally produced by introducing air for other fluidizing gas into the bottom of the coating container under conditions sufficient to fluidize the particulate coating material contained therein.

While such treatments have been successful in applying coatings to the surfaces of articles having relatively small dimensions, difliculties have been experienced when the articles to be coated possess relatively large dimensions, the fluidizing gases thus introduced being capable of producing a fluidized bed of only a limited depth.

It is therefore among the objects of the present invention to provide an apparatus and method for effecting the complete coating of an elongated article, e.g., a piece of pipe or tubing, with a thermoplastic particulate material applied by means of a fluidized bed coating technique.

A further object of the invention is to provide such an apparatus and method for forming substantially uniform thickness coating layers on the interior of elongated hollow articles.

Other objects and advantages of the invention will be apparent from the following detailed description thereof, taken in connection with the accompanying drawing in which:

FIGURE 1 is a vertical section through one embodiment of the apparatus of the invention;

FIGURE 2 is a partial vertical section through a further embodiment thereof; and

FIGURE 3 is a horizontal section viewed in the direc tion of line 3-3 in FIGURE 2.

In carrying out the coating method of the present invention the walls of an elongated hollow article are coated with a particulate thermoplastic material, e.g., nylon or polyethylene, by suspending the particles of the thermoplastic material in a fluidized bed formed adjacent the elongated article and heating the article at a temperature above the melting range of the thermoplastic material to fuse at least a portion of the thermoplastic particles to the article walls and thereby produce a coating thereon. In accordance with my invention, the fluidized bed is produced by depositing a mass of the thermoplastic material adjacent the hollow article and introducing a fluidizing gas, e.g., air, into the particulate mass adjacent the base thereof and at a plurality of points displaced longitudinally of a mass to thereby provide the desired fluidized bed throughout the entire length of the walls of the article to be coated.

By thus introducing the fluidizing gas at points intermediate the length of the walls of the article to be coated, a fluidized mass is maintained throughout a far greater depth States Patent "ice than Was heretofore found possible, employing conventional fluidized coating equipment in which a fluidizing gas is introduced adjacent the base of the reaction zone. The maintenance of a fluidized bed throughout the length of the article to be coated and the consequent production of a coating having a substantially uniform thickness, is thus assured.

It will be understood that, while the following specific description is directed to the coating of the internal walls of elongated articles, the invention is similarly applicable to the external coating of such articles by placing them in the fluidized bed formed as described hereinafter extending throughout the entire length of the articles to be coated.

Turning to the drawing, an apparatus 10 is illustrated in FIGURE 1 for providing a coating on the inside surface 12 of an elongated tube or pipe 11. The pipe 11 is maintained in a vertical position by means of a clamp 13 securing the pipe at the upper end 14 thereof, and a base 15 so shaped as to support the lower end 16 of the pipe. The clamp 13 may be supported, for example, by an arm 13' which may be secured in turn to any suitable conveying or transfer device.

The base 15 includes an upwardly extending plug section 17 shaped to substantially seal the lower end 16 of the pipe 11 when assembled therewith. A plurality of passageways 18 and 19 are defined Within the plug section 17, connected to pressurized gas lines 21 and 22, respectively. The passageways 18 and 19, it will be noted, communicate with the base of an elongated chamber 23 defined within the pipe 11 above the plug section 17.

A further passageway 24 extends through the walls of the base 15 communicating at one end with the base of the chamber 23 and at the opposite end with a pressurized gas line 25. Mounted within and extending axially of the chamber 23 is an elongated tube 26, the lower end of which is connected to passageway 24. A number of holes 27 are provided along the length of the tube 26, opening outwardly and upwardly from the tube to permit air or other fluidizing gas passed through line 25 into passageway 24 and through the elongated tube 26 to effect the production of a fluidized bed lengthwise of the chamber 23, as described in more detail hereinafter.

An induction coil 28 is illustrated, circumscribing the pipe 11 and movable longitudinally thereof on a support 29. The support 29 may be supported, for example, by an arm 29' which may be secured in turn to any suitable power-driven dolly or fixture.

In operation, the pipe 11 may be preheated to a desired ported by the supporting arm 13 therefor into position on base 15 as illustrated in the drawing. The pipe 11, the lower end 16 of which is plugged by plug section 17, is thereafter filled to a predetermined height with a quantity of powdered or pulverized plastic particles 31, e.g., constituted of nylon or polyethylene.

The walls 12 of the pipe 11 may be maintained at a temperature in excess of the melting range of the thermoplastic material by additionally utilizing the heating coil 28 and traversing the same lengthwise of the pipe 11 during the coating operation. By appropriately adjusting the energy dissipated and the rate of traversal of the induction coil longitudinally of the pipe, the internal wall 12 thereof is maintained at a substantially uniform temperature to thereby facilitate the production of a uniform coating thereon.

Upon feeding air through gas lines 21 and 22 through passageways 18 and 19, and into the base of the mass of plastic particles 31, a fluidized bed is produced in the lower portion of the chamber 23. In accordance with the invention, air is fed through pressure line 25, passageway 24, and tube 26, and introduced into the mass of plastic par- 7 ticles 31 at a number of spaced points along the length of the tube, adjacent the openings 2.7 therein.

The introduction of the fiuidizing gas at many points intermediate the length of the chamber 23 maintains the plastic particles 31 in the iluidized state throughout the length of the chamber. it has been found that, by thus maintaining a fluidized bed lengthwise of the walls 12 to be coated, the plastic particles do not cake or deposit unevenly or create unequal heat distribution, thus preventing localized melting or fusing of varying amounts of the plastic particles. Only the particles adjacent the walls fuse thereon, forming a coating having a substantially uniform thickness, and this without melting or changing the state of the particulate thermoplastic material in'the core of the fluidized bed.

After the coating action is completed, the induction coil 28 may be disengaged from the pipe ll, the pipe inverted and the residual thermoplastic particles 31 removed therefrom by gravity, or by an appropriate air blast. The resulting coated article possesses a substantially uniform plastic coating throughont the length of the Walls 12 thereof.

As shown in FEGURES 2 and 3, the elongated tube 26 may be replaced by a plurality of such tubes 26a, 26b, 26c and 26d mounted. for example, in a circular array, the holes in the several tubes directing the air, or other iiuidizing gas passed therethrough, upwardly and outwardly to produce the desired uniform fluidized bed throughout the length of the walls 12a to be coated.

Since the foregoing and other changes may be made in the specinc embodiment of the apparatus and method de scribed above, without departing from the scope of the invention, it is intended that the preceding description and the accompanying drawing be taken as illustrative and not in a limiting sense.

1 claim:

it. In a method of coating the walls of an elongated article with a particulate thermoplastic material, which comprises suspending the particles of said material in a fluidized bed formed concentrically of said elongated article and heating the same at a temperature above the melting range of the thermoplastic material to fuse a portion of said material to said walls to produce a coating thereon, the improvement comprising producing said fluidized bed by depositing a mass of said thermoplastic material concentrically of said article adjacent one end thereof and simultaneously introducing a iluidizing gas into the particulate mass adjacent said end and at a plurality of points displaced longitudinally of the article to thereby provide a fluidized bed extending lengthwise of the walls of said elongated article.

2. In a method of coating the inside walls of an elongated hollow article with a particulate thermoplastic material, which comprises suspending the particles of said ma terial in a fluidized bed formed within the elongated article and heating the same at a temperature above the melting range of the thermoplastic material to fuse a portion of said material to said walls to produce a coating thereon, the improvement comprising producing said fluidized bed by depositing a mass of said thermoplastic material within said article adjacent one end thereof and introducing a r'luidizing gas into the particulate mass adjacent said end and at a plurality of points disposed Within said article longitudinally thereof to thereby provide a fluidized bed "1 formed adjacent to and extending l ngthwise of the inside walls of said elongated article.

3. The method as defined in claim 2, in which the particulate thermoplastic ma erial is selected from the group consisting of nylon and polyethylene.

4. A method of coating the inside walls of an elongated piece of pipe or tubing with a particulate thermoplastic material which comprises:

(a) depositing a mass of said material within the chamber defined within said walls;

(b) feeding air from adjacent the base of said chamber upwardly through the mass of particulate material to fluidize the same in the region abutting the lower portion of the length of said walls;

(0) feeding air from a plurality of points disposed longitudinally of said mass upwardly and outwardly of said mass to effect fluidiz ation of the particulate mass throughout said chamber, thereby producing a fluid ized bed abutting the inside walls of the pipe or tubing and extending lengthwise thereof; and

(d) heating the inside walls at a temperature above the melting range of the thermoplastic material to fuse a portion of such material to said walls and produce a coating having a uniform thickness thereon.

5. An apparatus for coating the walls of an elongated piece of pipe or tubing, which comprises:

(a) a base for supporting said pipe or tubing in position for coating operations;

(b) a plurality of passageways defined Within said base for feeding a iiuidizing gas therethrough and into the base or" a chamber defined by the Walls of said pipe or tubing and said base;

(c) a further passageway defined within said base for feeding a fluidizing gas therethrough;

(d) a tube connected to said further passageway and disposed axially of said chamber, said tube having a plurality of spaced apart openings therein displaced along its entire length; and

(e) external heating means for heating the walls of said pipe or tubing to a temperature above the melting range of said thermoplastic material, said means being movable longitudinally of the elongated pipe or tubing for effecting fusing of the particulate material throughout the length of said walls to produce a coating having a uniform thickness thereon.

References Cited by the Examiner UNITED STATES PATENTS OTHER REFERENCES Kunststolfe ED 47, 1957, pp. 510412, ll7FB. WILLIAM D. MARTIN, Primary Examiner.

JOSEPH B. SPENCER, Examiner. 

1. IN A METHOD OF COATING THE WALLS OF AN ELONGATED ARTICLE WITH A PARTICULATE THERMOPLASTIC MATERIAL, WHICH COMPRISES SUSPENDING THE PARTICLES OF SAID MATERIAL IN A FLUIDIZED BED FORMED CONCENTRICALLY OF SAID ELONGATED ARTICLE AND HEATING THE SAME AT A TEMPERATURE ABOVE THE MELTING RANGE OF THE THERMOPLASTIC MATERIAL TO FUSE A PORTION OF SAID MATERIAL TO SAID WALLS TO PRODUCE A COATING THEREON, THE IMPROVEMENT COMPRISING PRODUCING SAID FLUIDIZED BED BY DEPOSITING A MASS OF SAID THERMOPLASTIC MATERIAL CONCENTRICALLY OF SAID ARTICLE ADJACENT ONE END THEREOF AND SIMULTANEOUSLY INTRODUCING A FLUIDIZING GAS INTO THE PARTICULATE MASS ADJACENT SAID END AND AT A PLURALITY OF POINTS DISPLACED LONGITUDINALLY OF THE ARTICLE TO THEREBY PROVIDE A FLUIDIZED BED EXTENDING LENGTHWISE OF THE WALLS OF SAID ELONGATED ARTICLE. 